For the fullscreen bug in Ubuntu, install CompizConfig Settings Manager and check "Legacy Fullscreen Support" under Utility>Workarounds like opossums said earlier.

And if you have Bumblebee installed, do the following:
1- Run <i>gksudo gedit /usr/local/games/Trine2/bin/trine2_bin_starter.sh</i> in terminal.
2- Add optirun to the script:
#!/bin/sh
cd /usr/local/games/Trine2
<b>optirun</b> bin/trine2_linux_32bit

I have just finished Trine and I didn't think twice before purchasing Trine 2 in the 50% off sale. I just wanna say thank you Frozenbyte for bringing Linux support to such a beautiful and fun game. You now have another loyal customer for at least the next 10 sequels. =)